Modeling Home Heating Systems With Circuit Simulation Software

July 1, 2024 by Bryan Cockfield 6 Comments

Electricity flow is generally invisible, silent, and not something that most humans want to touch, so understanding how charge moves around can be fairly unintuitive at first. There are plenty of analogies to help understand its behavior, such as imagining a circuit as a pipe of water, with pressure standing in for voltage and flow standing in for current. But you can flip this idea in reverse and use electric circuits to model other complex phenomena instead. [Oxx], for example, is using circuit theory to model his home’s heating systems.

To build his model, he’s using LTSpice, a free circuit simulation program. Using voltage to model temperature and current to model heat flow, he’s set up a model for his home to compare the behavior of a heat pump and a propane furnace. A switch model already in LTSpice with built-in hysteresis takes the place of the thermostat. Using temperature data for a single day in January [Oxx] can see how each of his two heating systems might behave, and the model for the heat pump is incredibly close to how the heat pump behaved in real life.

The model includes all kinds of data about the system, including the coefficient of performance of the heat pump and its backup electric resistive heater, and the model is fairly accurate at predicting behavior. Of course, it takes a good bit of work to set up the parameters for all of the components since our homes and heating systems won’t be included in LTSpice by default, but it does show how powerful an electric circuit analog can be when building models of other systems. If you’ve never used this program before, we’ve featured a few guides to getting started that you can take a look at.

Thanks to [Jarvis] for the tip!

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Radio Waves Bring The Heat With This Microwave-Powered Forge

April 18, 2023 by Dan Maloney 50 Comments

Depending on the chef’s skill, many exciting things can happen in the kitchen. Few, however, grab as much immediate attention as when a piece of foil or a fork accidentally (?) makes it into the microwave oven. That usually makes for a dramatic light show, accompanied by admonishment about being foolish enough to let metal anywhere near the appliance. So what’s the deal with this metal-melting microwave?

As it turns out, with the proper accessories, a standard microwave makes a dandy forge. Within limits, anyway. According to [Denny], who appears to have spent a lot of time optimizing his process, the key is not so much the microwave itself, but the crucible and its heat-retaining chamber. The latter is made from layers of ceramic insulating blanket material, of the type used to line kilns and furnaces. Wrapped around a 3D printed form and held together with many layers of Kapton tape, the ceramic is carefully shaped and given a surface finish of kiln wash.

While the ceramic chamber’s job is to hold in heat, the crucible is really the business end of the forge. Made of silicon carbide, the crucible absorbs the microwave energy and transduces it into radiant heat — and a lot of it. [Denny] shares several methods of mixing silicon carbide grit with sodium silicate solution, also known as water glass, as well as a couple of ways of forming the crucible, including some clever printed molds.

As for results, [Denny] has tried melting all the usual home forge metals, like aluminum and copper. He has also done brass, stainless steel, and even cast iron, albeit in small quantities. His setup is somewhat complicated — certainly more complex than the usual propane-powered forge we’ve seen plenty of examples of — but it may be more suitable for people with limited access to a space suitable for lighting up a more traditional forge. We’re not sure we’d do it in the kitchen, but it’s still a nice skill to keep in mind.

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Real Minecraft Furnace Generates Electricity From Coal

November 18, 2022 by Lewin Day 22 Comments

There’s a furnace in Minecraft that is used to power all kinds of things in the game. [Joel] of Joel Creates decided he wanted to build a real-world replica, and did exactly that.

The furnace consists of a 30 cm aluminium cube, inside which the coal is burned. Thermoelectric generators (TEGs) are then placed on the sides of the furnace to turn the heat into useful electricity. The TEGs are installed in a sandwich of aluminium plates designed to maximize heat transfer through the TEGs themselves. They’re fitted with heatsinks to help create the maximum thermal gradient for greater power output. The entire setup is housed in a larger aluminium cube that’s finished to look like the Minecraft furnace — achieved by using a CNC machine to draw on the aluminium with high-temperature Sharpies.

With the coal a-burning inside, the furnace was able to generate enough power to run its own cooling and exhaust fans. It even had a little power left over to charge a phone. Overall though, [Joel] hopes that with some improvement, it can one day power his Minecraft car replica up to its top speed of 25 mph.

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Replica Minecraft Furnace Actually Powers The Game

March 5, 2022 by Dan Maloney 3 Comments

Let’s face it, we all need a little distraction sometimes, especially lately. And for our money, there’s no better way to put your brain in park than to start up a Minecraft world and get to digging. The simple graphics, the open world, and the lack of agenda other than to find resources and build things are all very soothing.

But play the game long enough and you’re bound to think about what it would be like if the game world crossed over into the real world. The ironically named [Michael Pick] did just that when he managed to craft a real Minecraft furnace that can actually power the game. Of course, there are some liberties taken with the in-game crafting recipe for a furnace, which is understandable for a game that allows you to punch trees with a bare fist to cut them down.

Rather than using eight blocks of cobblestone to build his furnace, [Michael] made a wooden shell for a commercial folding camp stove. Insulated from the shell by a little cement board, the furnace looks pretty true to the in-game item. To generate the electricity needed to run the game, he used a pair of thermoelectric camping generators. With the stove filled with wood — presumably un-punched — the generators put out enough juice to at least partially charge a battery bank, which was then used to power a Raspberry Pi and 7″ monitor. His goal was to get enough power from the furnace to do a speed run in the game and find three diamonds to build a diamond pickaxe. Honestly, we’re jealous — our first diamonds never come that easy.

We’ve seen other Minecraft-IRL crossovers before. Fancy a ride in a minecart? We’ve got that covered. Or maybe you’d rather control a desk lamp from within the game? That’s a thing, too.

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Flip-Top Foundry Helps Manage The Danger Of Metal Casting

September 11, 2021 by Dan Maloney 18 Comments

Melting aluminum is actually pretty easy to do, which is why it’s such a popular metal for beginners at metal casting. Building a foundry that can melt aluminum safely is another matter entirely, and one that benefits from some of the thoughtful touches that [Andy] built into his new propane-powered furnace. (Video, embedded below.)

The concern for safety is not at all undue, for while aluminum melts at a temperature that’s reasonable for the home shop, it’s still a liquid metal that will find a way to hurt you if you give it half a chance. [Andy]’s design minimizes this risk primarily through the hands-off design of its lid. While most furnaces have a lid that requires the user to put his or her hands close to the raging inferno inside, or that dangerously changes the center of mass of the whole thing as it opens, this one has a fantastic pedal-operated lid that both lifts and twists. Leaving both hands free to handle tongs is a nice benefit of the design, too.

The furnace follows a lot of the design cues we’ve seen before, starting as it does with an empty party balloon helium tank. The lining is a hydrid of ceramic blanket material and refractory cement; another nice safety feature is the drain channel cast into the floor of the furnace in case of a cracked crucible. The furnace is also quite large, at least compared to [Andy]’s previous DIY unit, and has a sturdy base that aids stability — another plus in the safety column.

Every time we see a new furnace design, we get the itch to start getting into metal casting. And with the barrier to entry as low as a KFC bucket or an old fire extinguisher, why not give it a try? Although it certainly pays to know what can go wrong before diving in.

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DIY Furnace Smelts Magnetite Sand Into An Impressive Chef’s Knife

March 9, 2021 by Mike Szczys 24 Comments

Some people order their raw materials from a factory, missing out on 99% of the fun… or suffering, we’re not sure which. To make that call, you need to look in on the process [IllyriaD] used to collect magnetite sand and turn it into a wicked-looking chef’s knife.

This began by collecting 150 pounds (!) of magnetic dirt from dry lake beds while hiking using a magnet pickup tool with release lever that he got from Harbor Freight. Several repeated magnetic refining passes separated the black ore from non-metallic sands ready for the furnace that he built. That is used to fire up the raw materials using 150 pounds of charcoal, changing the chemical composition by adding carbon and resulting in a gnarly lump of iron known as a bloom.

From there, it’s just a matter of beating the iron bloom into submission over at the anvil. [IllyriaD] details the process of flattening it out to a bar shape, then folding it over. Seven total folds are made for 128 layers, and in the gallery there’s a fantastic image that captures the striation when viewed on end. After being sharpened and polished, you can see where the bevel descends through those layers.

It’s delightful to see people working through the old ways and proving you don’t need a factory, as long as your true goal is to explore the process itself. Does this leave you wanting even more? [IllyriaD] left some insight about the process in the comments of the reddit thread. You probably also want to check out the tile-roofed hut built by [PrimitiveTechnology] without any modern tools.

An Efficient Homemade Wood Furnace

November 30, 2019 by Sharon Lin 17 Comments

For poor [workshop from scratch], winter brings the joy of a cold workshop. Since the building is structurally made from tin, warming up the room is difficult.

Naturally, the solution was to construct a homemade wood furnace. The build starts off with an angle grinder being taken to a compressed air tank. After sawing off the top and sanding down the edges, the builder slices out an opening and welds together some rods into a stand for the center. He then proceeds to weld some external frames for the furnace, as well as a chimney stack, some nifty covers joined by hinges, and a fan/temperature regulator to keep the fire going.

Most of the pieces seem to come from scrap metal lying around the workshop, although the degree to which the entire project comes together is quite smooth. Some filter and spray paint do the trick for cleaning up the furnace and making it look less scrappy. The last step? A stack of wooden logs and a blow torch to start the fun. Outside of the furnace, an LCD screen keeps track of the temperature, giving some feedback and control.

The result is perhaps a too effective at warming up the workshop, but the problem sure is solved!

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